1. Field of the Invention
This invention relates to a process for the preparation of a film-forming resin composition, and more particularly relates to a process for the preparation of a three dimensionally crosslinkable film-forming resin composition formed by graft polymerization of an alkoxysilane compound having a polymerizable unsaturated group onto a film-forming resin.
2. Description of the Prior Art
The thermoplastic resin such as polyvinyl chloride, phenoxy resin, and the like has been used in a coating composition. However, the aforementioned resins have such disadvantages as to have little or no reactive functional group for crosslinking reaction, and to be extremely difficult for a film to be crosslinked for curing, resulting in that the film formed therefrom is unsatisfactory in such properties as solvent resistance, corrosion resistance, water resistance, and the like.
In order to overcome the aforementioned defects of the resins having little or no reactive functional group for crosslinking reaction, Japanese Patent Application No. 14212/1982 discloses a process which comprises effecting a radical reaction of an alkoxysilane compound having an unsaturated group onto hydrogen and/or a halogen atom contained in the aforementioned resins and drawn by a radical in the presence of a free-radical initiator. According to the process of the aforementioned Japanese patent application, the alkoxysilane group is added to the skeleton of the resin, and the resulting addition product solution in an organic solvent is coated followed by hydrolyzing the alkoxysilane group to obtain a three dimensionally crosslinked and cured film. The crosslinked and cured film exhibits excellent properties in solvent resistance and water resistance as well as in physical properties, corrosion resistance, weather resistance, and the like.
That is, according to the aforementioned process, such resins as polyvinyl chloride resin and phenoxy resin, for which it is impossible or extremely difficult to form a three dimensionally crosslinked and cured film, can very easily be formed to a three dimensionally crosslinked film, resulting in remarkable improvements in water resistance, corrosion resistance, solvent resistance, weather resistance, physical properties, and the like without reduction in the excellent adherance which the aforementioned resins originally possess to plastics and metal.
However, according to the process of the Japanese patent application, it is rather difficult to carry out sufficiently the reaction between the alkoxysilane compound having an unsaturated group and the aforementioned resins, and consequently properties of the film formed therefrom are not expected to be remarkably improved. Thus, the aforementioned process has such disadvantages that the costly alkoxysilane compound is needed to be used in a large amount, that the reaction effected at high temperatures for a long period of time results in deterioration due to gelation or coloring of the resin, and that the process is economically undesirable when the aforementioned reaction is to be carried out sufficiently. Further, the aforementioned process has such a disadvantage that the resin used in the process is limited to relatively highly reactive resins having such a hydrogen and/or halogen atom as to be drawn by a radical.